1. Field of the Invention
The present invention relates to a functionalized fiber material which has a sustained discharge function for an agent creating a skin care effect with a resistance for washing without losing the feeling and the hygroscopic property essentially possessed by the fiber material itself, and a method for treating a fiber material to obtain it, wherein said functionalized fiber material can be suitably utilized in a fabricing field such as underwears and shirts.
2. Description of Related Art
Ascorbic acid is a natural antioxidant agent and widely used in cosmetics and foods for health for the purposes of skin care and preventing oxidation of foods. Applications of ascorbic acid to fiber products have been tried since before in order to obtain a function of skin care or deodorization. However, as ascorbic acid is oxidized very easily, it loses its antioxidant property within a short time even if it is simply added on a fiber, and is also poor in a resistance for washing if it is only simply added thereon. Accordingly, in the application of ascorbic acid to fibers, it has been important points to stabilize ascorbic acid and improve its resistance to washing when it is added on fibers.
For example, JP-B-3-13355 discloses a method for a deodorization treatment having a resistance for washing wherein ascorbic acid and various ferrous salts are fixed to a fiber using a synthetic resin. However, the method for fixing ascorbic acid to a fiber using a synthetic resin has weak points such as deterioration of a feeling of the fiber and spoiling a hygroscopic property essential to the fiber when natural fibers and cellulose fibers are treated. Further, as the methods intending to solve the instability of ascorbic acid, JP-A-10-131042 discloses a softening finishing agent which has small capsules encapsulating an antioxidant comprising an alkyl ester of ascorbic acid in order to add a deodorizing function, and JP-A-10-331070 discloses an antioxidant fiber material, wherein an antioxidant is stabilized by forming a complex between the antioxidant and a protein, and a fiber product is treated with said complex.
A fiber finishing composition disclosed in JP-A-10-131042 has a superior stability because an ascorbic acid derivative is used, but is poor in a durability because the composition of said invention has been designed as a softening finishing agent to be used after washing without taking account of a resistance to washing at all. Furthermore, an antioxidant fiber material described in JP-A-10-331070 is the one intended for an application field of a food packaging materials, and has no function of sustained discharge because it has been treated together with a cross-linking agent to improve a durability, although it has a stabilized antioxidant and an acceptable resistance to washing.
On the other hand, JP-A-5-32537 discloses derivatives of a compound such as ascorbic acid, phosphoric ester of ascorbic acid and sulfuric ester of ascorbic acid, used for a skin care cosmetics as a substance having an action to promote a collagen synthesis, but this cosmetic does not have a function of sustained discharge of ascorbic acid to skin.
An object of the present invention is to provide a functionalized fiber material having a skin care effect without losing the feeling and the hygroscopic property which are essentially possessed by the fiber.
Another object of the present invention is to provide a fiber material which allows a sustained discharge of an ascorbic acid derivative stuck on the fiber product by an action of a fat component such as sebum present on a skin surface of the human body.
Further object of the present invention is to provide a fiber material on which an ascorbic acid derivative having a resistance to washing sticks.
Still further object of the present invention is to provide a method for treating a fiber material to obtain said fuctionalized fiber material.
The present invention consists of a functionalized fiber material treated with an emulsion containing an ascorbic acid derivative which is hardly soluble in water, and said ascorbic acid derivative which is hardly soluble in water is preferably a polyalkylester of L-ascorbic acid. The treatment method comprises addition of an emulsion containing an ascorbic acid derivative which is hardly soluble in water on the fiber material, wherein said emulsion comprises a mixture of an ascorbic acid derivative which is hardly soluble in water, an anionic surfactant optionally together with a nonionic surfactant and water, and the concentration of the ascorbic acid derivative which is hardly soluble in water in said emulsion is from 0.05 to 10% by weight.
The fiber materials used in the present invention are not specially limited. The fiber materials may be natural fibers such as cotton, wool, silk and etc., regenerated fibers such as rayon, polynosic, cellulose acetate and etc., synthetic fibers such as polyester, nylon, acrylic and etc. or combined filaments made of one or more kinds thereof, which are usually used as fabricing and knitting. Further, in the case of the regenerated fiber or the synthetic fiber, it may include a fiber material containing a substance to express other functions. Said substance contained in the fiber material is not specially limited so long as it does not disturb the sustained discharge function of the ascorbic acid derivative.
In the case of the rayon or the polynosic, the fiber material may include a modified regenerated cellulose fiber having an improved resistance to swelling with water, which is obtained by adding and mixing a cross-linking agent into a cellulose viscose solution then spinning said solution, or a modified regenerated cellulose fiber having an improved resistance to swelling with water and fibrillation character, which is obtained by adding and mixing a cross-linking agent into a cellulose viscose solution then spinning said solution followed by contacting with an aqueous solution of a cross-linking agent.
In the above case, in order to express other function such as antibacterial action, deodorization action and an improved dyeability, a functionalizing agent such as fine granular chitosan, fine balloon particles, anionizing agent can, of course, be used together with the cross-linking agent. Form of the fiber material may be any of raw fiber, spun yarn, knitted or woven fabric, and fiber product. Furthermore, the fiber material with each of the above forms may have been treated in advance to give another function so long as the treatment does not inhibit the sustained discharge of the ascorbic acid derivative, but in this case, said treatment should be applied preferably before the treatment of the present invention, and particularly said treatment using a cross-linking agent must be applied before the treatment of the present invention. In the case when the fiber material is raw fiber, spun yarn, or knitted or woven fabric, they are used as a sewing fiber material for fabricing.
The ascorbic acid derivative which is hardly soluble in water to be used in the present invention is not specially limited so long as the derivatives which are soluble in an organic solvent, and includes, for example, monoalkylesters of L-ascorbic acid, dialkylesters of L-ascorbic acid, trialkylesters of L-ascorbic acid, tetraalkylesters of L-ascorbic acid and the like. Among them, tetraalkylesters of L-ascorbic acid is preferable from the viewpoint of a resistance to washing and a stability. The tetraalkylesters of L-ascorbic acid includes a isopalmitoyl or a stearoyl derivative.
The surfactants to be used for emulsifying the above described ascorbic acid derivative are desirably an anionic surfactant. When an ascorbic acid derivative can not be sufficiently emulsified due to an lower emulsifying power by using an anionic surfactant alone, a nonionic surfactant can be used as in a combination with the anionic surfactant. The anionic surfactants to be used in the present invention are not specially limited, and includes, for example, a various kinds of fatty acid soaps, sodium lauryl sulfate, sodium higher alcohol sulfate, sodium dodecylbenzenesulfonate, sodium dialkylphosphosuccinate, potassium alkylphosphate, sodium polyoxyethylenealkylether sulfate, and the like. Further, the nonionic surfactants which can be used in the present invention include, for example, polyoxyethylene derivatives, sorbitan monoalkylates, sorbitan dialkylates, sorbitan trialkylates and the like. The nonionic surfactant can be suitably selected from the above group.
The method for treating a fiber material of the present invention comprises, firstly obtaining an emulsion containing an ascorbic acid derivative which is hardly soluble in water by mixing, stirring and emulsifying the ascorbic acid derivative and water, dipping a fiber material therein, squeezing the fiber material at the squeezing rate from 60 to 120%, subsequently drying at the temperature from 80 to 200xc2x0 C. for the time from 1 to 30 minutes. The mean for adding the emulsion containing an ascorbic acid derivative on the fiber material may be coating or spraying the emulsion as well as dipping therein to stick on the fiber material.
A fabric can be made of a modified regenerated cellulose fiber with an improved swelling property to water, which is obtained by adding and mixing a cross-linking agent to a cellulose viscose solution then spinning said solution, subsequently said fabric can be treated with a cross-linking agent in order to jointly improve a fibrillation character. In such a treatment, if said treatment with a cross-linking agent is conducted after the treatment with an emulsion of the ascorbic acid derivative of the present invention, the cross-linking agent reacts with the ascorbic acid derivative and a regenerated cellulose fiber, resulting in reducing the sustained discharge function of an ascorbic acid derivative by an action of a sebum and the like. Accordingly, said treatment with a cross-linking agent must be conducted before the treatment with an emulsion of the ascorbic acid derivative of the present invention.
Concerning to the concentration of the emulsion to be used for treating a fiber material, the concentration of the ascorbic acid derivative in the emulsion is preferably in the range from 0.05 to 10% by weight. The concentration lower than 0.05% by weight can not exhibit an expected skin care effect, and the concentration over 10% by weight unsuitably increase a viscosity of the emulsion and make it difficult to treat a fiber material evenly. The concentration of the surfactant in this process is not specially limited so long as it enables to emulsify. However, the concentration is preferably as low as possible within a range enabling to emulsify, because too much surfactant to an amount of an ascorbic acid derivative deteriorates a resistance to washing. The method for stirring to obtain the emulsion is not specially limited, and, for example, stirring with a homogenizer may be used.
Furthermore, in emulsifying, though an ascorbic acid derivative can be emulsified only with a surfactant, an addition of an organic solvent can be employed in order to adjust a concentration and a viscosity of the emulsion. The organic solvent to be used is not specially limited so long as it can dissolve the ascorbic acid derivative, and includes, for example, oleic acid, squalane and derivatives thereof, hexane, diethylether, ethyl acetate, dodecanol, and the like.
As obvious from the examples described hereinunder, when tetraalkylesters of L-ascorbic acid as an ascorbic acid derivative which is hardly soluble in water is used for treating a fiber material by the treatment method of the present invention, the stuck amount of the tetraalkylesters of L-ascorbic acid on a fiber material before washing in the range from 0.30 to 48.0 mg/g gives a functionalized fiber material which is excellent in a sustained discharge function and moisture absorption and release properties.
The ascorbic acid derivative stuck on a fiber material according to the present invention shows an excellent resistance to washing in such an extent that 50% or more of the initial amount remains even after 10 times of washings. This is because a hydrophilic property of the derivative is very weak. When an ascorbic acid derivative is used in cosmetics, this derivative is usually incorporated into a skin layer and regenerate an ascorbic acid by an action of an enzyme to express the effect. The ascorbic acid derivatives stuck on a fiber material do not express an expected antioxidant property in a condition as stuck on a fiber, but once the fiber product is worn, the derivative is discharged slowly on a skin by an action of a fat such as sebum of the wearer and incorporated into a skin finally to express the effect.
According to the present invention, falling off of the ascorbic acid derivatives by washing can be suppressed, and in addition, it is presumed that a skin care effect can be expressed by discharging said derivatives gradually on a skin by an action of a fat component such as sebum present on a skin surface of the human body, and being incorporated into a skin layer since said derivatives are well dissolved in a fat such as sebum. Furthermore, The treatment of the present invention does not give any change in a feeling and moisture absorption release properties possessed by the fiber material.